"There is no justice here," said the libertarian and potential 2016 GOP presidential candidate. "It is wrong and it needs to change."

Paul recounted from memory to a hearing of the Senate Judiciary Committee several cases he said he'd learned about where mandatory minimums had resulted in a miscarriage of justice.

He said one man, Edward Clay, was arrested with less than 2 ounces of cocaine. Even as a first-time offender, he was sentenced to 10 years in prison because of mandatory sentencing guidelines, Paul said.

"Each case should be judged on its own merits," Paul said. "Mandatory minimums prevent this from happening."

Paul said when he described the effects of mandatory minimum sentences, "you might think I was talking about Jim Crow laws. The war on drugs is disproportionately affecting black males."

He was referring to post-Civil War laws that effectively preserved racial segregation and unfair treatment for minorities.

Paul has drafted legislation with Senate Judiciary Committee Chairman Patrick Leahy to give judges wider latitude to craft their own sentences as one way to relieve prison overcrowding and bring down the exploding costs of running prisons. The committee is looking at that bill and another that focuses on waiving mandatory minimum prison terms in some drug cases.

There are more than 218,000 federal prisoners, according to the Bureau of Justice Statistics, a number that grown from about 25,000 federal prisoners in the 1980s, when many mandatory penalties were put in place.

Wednesday's hearing was the first step in what supporters hope will be legislative action by the end of the year. The Senate Judiciary Committee has not yet scheduled a meeting to discuss the bills affecting mandatory sentences. But Leahy has said repeatedly he would like to press forward on the issue.

In the House, Reps. Bobby Scott, D-Va., and Thomas Massie, R-Ky., have introduced a version of Paul and Leahy's bill. But the chairman of the House Judiciary Committee, Rep. Bob Goodlatte, R-Va., has voiced skepticism. But a number of House Republicans have backed different reform efforts and have said they are watching closely what the Senate does.

At Wednesday's hearing, the committee heard from two supporters of reform efforts, Brett Tolman, a former U.S. attorney in Utah, and Marc Levin, the policy director for the Right on Crime Initiative at the Texas Public Policy Foundation.

But another witness, Scott Burns, the executive director of the National District Attorneys Association, said mandatory minimums had been a useful tool for state and local prosecutors and questioned the push to change them.

"Why now?" Burns said. "With crime at record lows, why are we looking at sweeping changes?"

Sen. John Cornyn, R-Texas said efforts to correct problems were noble, but "we have to be careful not to legislate by anecdote. We have all heard legal horror stories."

Leahy pleaded with his colleagues to work together on the issue, saying it is one of the most important the committee is considering. To bring home the impact, he asked a dozen or so family members of prisoners sentenced to mandatory minimums to stand up.

The family members, who had traveled from Montana, Texas, Utah and Illinois, among other places, stood and clutched photos of their loved ones as Leahy closed the committee hearing.